Hydraulic systems for vehicles

ABSTRACT

An anti-skid braking system includes hydraulically actuated valves which interrupt the supply of fluid to the brakes when deceleration is excessive, the pressure fluid for both the brakes and the actuators being supplied by a single pump driven by the vehicle starter motor, and means which control the pressure of the brake fluid and the actuator fluid to predetermined values.

United States Patent Ingram et al.

[ 1 HYDRAULIC SYSTEMS FOR VEHICLES [72] Inventors: Brian Ingram, Warks;Douglas Roy Spence, Warks; Robin Adam gochrane Warks, all of England[73] Assignee: Girling Limited, Birmingham, England [22] Filed: Dec. 8,1970 21 Appl. 106.; 96,085

[52] US. Cl ..303/2l F [51] Int. Cl. ..B60t 8/06 [58] Field of Search..303/21 F [56] References Cited UNITED STATES PATENTS 3,532,391 10/1970Klein ..303/2l F [4 1 Sept. 12,1972

3,610,702 10/1971 MacDuff "303/511 3,521,931 7/1970 Leibel ..3oa/211=3,606,488 9/1971 Beuchle 61a] ..303l2lF Primary Examiner-Evan C. BlunkAssistant Examiner-H. S. Lane Attomey-lmirie and Smiley [5 7] ABSTRACTAn anti-skid braking system includes hydraulically actuated valves whichinterrupt the supply of fluid to the brakes when deceleration isexcessive, the pressure fluid for both the brakes and the actuatorsbeing supplied by a single pump driven by the vehicle starter motor, andmeans which control the pressure of the brake fluid and the actuatorfluid to predetermined values.

8 Claims, 3 Drawing Figures PATENTEUSEPIZIQYZ SHEET 2 [IF 2 a .m w 3ROB/N 4. C ocwm NE 1 HYDRAULIC SYSTEMS FOR VEHICLES BACKGROUND OF THEINVENTION In a hydraulic system for a vehicle of the kind in whichhydraulic fluid under pressure and under the control of a pedal-operatedmaster valve is supplied to at least one slave cylinder of at least onewheel brake through a normally open hydraulically actuated valve,anti-skid sensing means are operative to control a supply of hydraulicfluid under pressure, hereinafter referred to as the control pressure,to the actuator to cause the actuator to close its associated valve andthereby cut off the supply of fluid to the slave cylinder when thedeceleration to which the braked wheel is subjected exceeds apredetermined value.

Although the hydraulic fluid supplied by the master valve is at apressure sufficient to apply an effective braking effort to the brakedwheel, it is preferable that the pressure of hydraulic fluid supplied tothe actuator via the anti-skid device is maintained at an intermediatevalue which, although sufficient to effect 'closure of the actuator, isat a pressure substantially less than that of the brake applyingpressure.

In our US. application Ser. No. 73,081, the control pressure issuppliedby a pump and the braking pressure is supplied by manualoperation of the master cylinder. In order to increase the outputpressure of the master cylinder it can also be supplied with highpressure fluid from a pump, as described in our US. application Ser. No.77,708. Combining these two proposals to meet the preferred pressurerequirements of an antiskid system would lead to the use of separatepumps for the control pressure and the braking pressure. Since the pumpswould be located in the engine compartment or bonnet space of thevehicle, the arrangement would be uneconomical in its use of materialsand in its use of the limited space available in the engine compartmentor bonnet space.

SUMMARY OF THE INVENTION According to our invention, in an hydraulicsystem of the kind set forth for a vehicle, hydraulic fluid is sup pliedto both the master cylinder and the actuator from the output of a singledriven pump, pressure responsive means being located in the output'ofthe pump to cut off the supply to the actuator when a predeterminedcontrol pressure has been reached.

The pressure responsive means may also be arranged to stop the pump whena predetermined brake applying pressure has been reached which is higherthan the said control pressure.

Preferably the pump is driven by an electric motor, such as the startermotor for the engine of the vehicle. The motor is of the type in which agreater torque is developed at a lower speed of rotation and a smallertorque is developed at a higher speed of rotation. Thus, when the motoris operating ata lower speed, the pump is adapted to supply a'smallvolume of fluid at a higher pressure. When the motor is operating at ahigher speed, the pump is adapted to supply a larger volume of fluid butat a lower pressure.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a layout of a braking system fora vehicle incorporating a single pump to provide brake applying andcontrol pressures;

FIG. 2 is a modification of a portion of the layout shown in FIG. 1; and

FIG. 3 is a modified valve for incorporation in the braking systemillustrated in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION In the braking system illustratedin FIG. 1, a pedalcontrolled master valve 100 controls the supply offluid under pressure from a pump 101 to the slave-cylinders 16, 19 and20. The pump 101 also forms the source of control pressure fluid for thecontrol valves 30 and 31 and the actuators 32 and 34.

The pump 101 delivers fluid along line 109 to an hydraulic accumulator110 which is connected to the master valve 100 by line 111, the mastervalve 100 being connected to the pump reservoir 102 by return line 104.The pump 101 also delivers fluid along lines 115 and 113 to controlvalves 30 and 31 which are connected to the reservoir l02 by return line103. The pump 101 is driven from an electric motor 105 through a cam box106. The motor 105 is energized by an electrical storage battery 106athrough a switch 107.

The supply line 115 to the control valves is connected into the supplyline 109 to the accumulator 110 and non-return valves 108 and 108a arelocated in the line 109 upstream and downstream respectively of thisconnection.

In the supply line 115 there is located an isolating valve 117 and acombined relief and one-way valve 112 downstream of the isolating valve117. The valve 112 is set to relieve to reservoir 102 via line 114 whenthe control pressure exceeds a predetermined value. The isolatingvalve117 is controlled by a relay 118 which is connected in series with arelay 119 operating switch 107 in the motor circuit, battery 106a and alow pressure switch 116 sensitive to the pressure in the control circuitand located down stream of the relief and oneway valve 112.

A high pressure switch 120 sensitive to the pressure in the accumulator110 is located downstream of one way valve 108a and is connected acrossthe battery 106a and relay 119 and in parallel to relay 118 and lowpressure switch 116.

Therefore, on switching on the vehicle ignition, pressure switches 116and 120 both close and when either close, relay 119 is actuated to startmotor and pump 101. Also when switch 116 closes, relay 118 is actuatedto open isolating valve 117 to allow fluid to be supplied to the controlcircuit. When the control pressure and the brake applying pressure havereached a predetermined value, for example 500 p.s.i. the low pressureswitch 116 opens and de-energizes the relay 118 which allows theisolating valve 117 to close. The pump 101 continues to deliver fluid tothe accumulator until the brake applying pressure reaches apredetermined value, for example 2,500 psi. when the high pressureswitch opens and de-energizes the relay 1 19 to cut out the motor 105.Thereafter the motor 105 is energized and de-energized automatically ifeither the control pressure or the brake applying pressure drops belowtheir predetermined values since the pressure switches 116 and each forma circuit with the relay 119.

When the brakes are applied the deceleration of each front wheel issensed by an electrically inductive sensor 13, and the deceleration ofeach rear wheel is sensed by an electricallyinductive sensor 14.

When the deceleration of one of more wheels exceeds a predeterminedvalue the A.C. output from the sensor on that wheelor wheels in questionis fed to electronic control means which convert the A.C. signal into aDC. output, Specifically, the output from each sensor 13 is-fed to aseparate electronic control module 15, and the A.C. signals from thesensors 14 are fed to a common electric control module 17.

Each control valve 30 is adapted to regulate the supply of fluid to anactuator 32 for controlling the braking effort applied to one of thefront wheels of the vehicle in response to the DC. output signalreceived from the control module to which it is connected. The outputsignals from each control module 15 are responsive to the decelerationof the front wheel with which that module 15 is associated.

The control valve 31 is adapted to regulate the supply of fluid from thesecond circuit to an actuator 34 for controlling the braking effortapplied to the rear wheels of the vehicle in response to the DC. outputsignal received from the control module 17. The output signals from thecontrol module 17 is responsive to the deceleration of the rear wheelsof the vehicle.

In the modified layout illustrated in FIG. 2, the pressure switches 116and 120, the isolating valve 117 and the combined relief and one wayvalve 112 are replaced by a single high pressure switch 120a located inthe pump delivery line 115 and a pressure control valve assembly 121 inline 115 down stream of the switch 120a. The relief line 114 is omittedbut the remainder of the layout is identical with that shown in FIG. 1so that it need not be illustrated or described further herein.

In this modified construction, where corresponding reference numeralshave been used to indicate corresponding parts, the pressure controlvalve assembly comprises a housing 122 provided with a chamber 123connected between the line 115 and the line 113 to the control valves 30and 31 and the actuators 32 and 34. A head 124 carried by a stem 125 ofa tipping valve is adapted to be urged by a spring 126 into engagementwith a seating in the housing to control fluid flow into the chamber 123from the line 115. The head 124 normally is held in a tipped positionwith respect to the seating by the action of a spring loaded plunger 127acting on the stem 125 through a head 128 of substantial diameter at itsinner end which is located within the chamber 123.

When the pump 101 is operating, fluid under pressure is pumped to thehydraulic accumulator 110 and the chamber 123 through the line 109 andthe line 115 until the pressure in the chamber 123 attains apredetermined value, for example 500 p.s.i. The pressure in the chamber123 acts on the head 128 and, upon the said predetermined pressure beingattained, the plunger 127 is moved against its spring loading to permitthe head 124 of the tipping valve to close under the influence of thespring 126. Fluid is then pumped only to the hydraulic accumulator 110until the pressure attains a predetermined value, for example 2,500

1 p.s.i., whereupon the pressure switch 120a opens to de- The pressurecontrol valve 121 illustrated in FIG. 2 may be replaced by a valve ofthe construction illustrated in FIG. 3. The valve illustrated in FIG. 3comprises a cylindrical housing 130 which is closed at opposite ends andin which works a valve spool 131. The valve spool 131 is provided at anintermediate point in its axial length with a diametrical passage 132leading through an axial passage 133 into the upper end of the housing130 towards which the valve spool 131 is urged by a compression spring134 acting between the opposite lower end of the valve spool 131 and thehousing 130. The valve spool 131 is provided at an intermediate point inits length between the passage 132 and its lower end with an annularrecess 135 which is normally aligned, at least partially, with anannular recess 136 in the wall of the housing 130 leading to the line113. When the valve spool 131 is in its normal open position the lineleads into the annular recess 135 so that the line 115 delivers fluid tothe line 113 through the recesses 135 and 136. Fluid pressure in thediametrical passage 132 is relieved to the upper end of the housing sothat this pressure acts downwardly over the full area of spool 131. Whenthe pressure attains a predetermined value, for example 500 p.s.i. thevalve spool 131 moves downwardly against the loading of the spring 134,into the position shown, to cut off communication between the recessesand 136.

The construction and operation of the embodiment is otherwise the sameas that of the embodiment of FIG. 2 and need not be described furtherherein.

The electric motor 105 conveniently is the starter motor for the engineof the vehicle. A characteristic of such a motor is that greatest torqueis developed at low speed so that at low speed the pump driven by themotor is adapted to supply a small volume of fluid at high pressure.Whereas at a higher speed of rotation of the motor, the pump is adaptedto supply a larger volume of fluid at a lower pressure. Since thehydraulic system described requires relatively large fluid volumes at,say, 500 p.s.i. for the control circuit and relatively smaller volumesof fluid at, say, 2,500 p.s.i., for the braking circuit, an electricstarter motor is able to fulfill both these requirements.

The pump could be driven by its own electric motor or directly from theengine of the vehicle, through it is preferable for the motor to beindependent of the engine which may stall or be idling during a skid.

What we claim is:

1. A vehicle brake hydraulic system comprising a single driven pump, apedal operated master valve for controlling a high pressure supply offluid from the pump to at least one slave cylinder of at least one wheelbrake, a normally open valve having a fluid actuator through which valvepasses the fluid supply to the at least one slave cylinder, anti-skidsensing means for controlling a by-pass supply of fluid from the pump tothe actuator to cause its valve to close and thereby cut off the supplyof fluid to the at least one slave cylinder when the deceleration towhich the braked wheel is subjected exceeds a predetermined value, thefluid supply passed by said actuated valve being at a lower controlpressure, and pressure responsive means located in the output of thepump to cut off the fluid supply for the actuated valve when apredetermined control pressure has been reached.

2. A system as in claim 1 wherein the pressure responsive means areoperative to stop the pump when a predetermined brake applying pressurehas been reached which is higher than the said control pressure.

3. A system as in claim 2, wherein the pump is driven by the startermotor of the vehicle.

4. A system as in claim 2 wherein a pressure switch is located in thepump output to make and break an electrical circuit controlling theoperation of the pump in response to variations in the brake applyingpressure about the predetermined value.

5. A system as in claim 4, wherein a second pressure switch is locatedin the fluid supply to the fluid actuated valve to make and break anelectrical circuit controlling the operation of a valve adapted toisolate the actuated valve from the pump, said second pressure switchbeing responsive to variations in the control pressure above thepredetermined value.

6. A system as in claim 4, wherein a control valve is located in thefluid supply to the actuator to isolate or connect the actuator to thepump in response to variations in the control pressure above thepredetermined value.

7. A system as in claim 6, wherein the control valve is a pressureresponsive tipping valve.

8. A system as in claim 6, wherein the control valve is a pressureresponsive spool valve.

1. A vehicle brake hydraulic system comprising a single driven pump, apedal operated master valve for controlling a high pressure supply offluid from the pump to at least one slave cylinder of at least one wheelbrake, a normally open valve having a fluid actuator through which valvepasses the fluid supply to the at least one slave cylinder, anti-skidsensing means for controlling a by-pass supply of fluid from the pump tothe actuator to cause its valve to close and thereby cut off the supplyof fluid to the at least one slave cylinder when the deceleration towhich the braked wheel is subjected exceeds a predetermined value, thefluid supply passed by said actuated valve being at a lower controlpressure, and pressure responsive means located in the output of thepump to cut off the fluid supply for the actuated valve when apredetermined control pressure has been reached.
 2. A system as in claim1 wherein the pressure responsive means are operative to stop the pumpwhen a predetermined brake applying pressure has been reached which ishigher than the said control pressure.
 3. A system as in claim 2,wherein the pump is driven by the starter motor of the vehicle.
 4. Asystem as in claim 2 wherein a pressure switch is located in the pumpoutput to make and break an electrical circuit controlling the operationof the pump in response to variations in the brake applying pressureabout the predetermined value.
 5. A system as in claim 4, wherein asecond pressure switch is located in the fluid supply to the fluidactuated valve to make and break an electrical circuit controlling theoperation of a valve adapted to isolate the actuated valve from thepump, said second pressure switch being responsive to variations in thecontrol pressure above the predetermined value.
 6. A system as in claim4, wherein a control valve is located in the fluid supply to theactuator to isolate or connect the actuator to the pump in response tovariations in the control pressure above the predetermined value.
 7. Asystem as in claim 6, wherein the control valve is a pressure responsivetipping valve.
 8. A system as in claim 6, wherein the control valve is apressure responsive spool valve.